1. Field of the Invention
This invention relates generally to a system and method for estimating vehicle states and, more particularly, to a system and method for estimating vehicle roll-rate, vehicle roll angle, vehicle lateral velocity and vehicle yaw-rate for rollover reduction purposes.
2. Discussion of the Related Art
It is known in the art to provide vehicle control enhancement using differential braking control, rear-wheel steering control, front-wheel steering control, or any combination thereof to help prevent a vehicle from encountering conditions that present an increased possibility of rollover. These systems may receive vehicle dynamics information from various sensors, such as yaw rate sensors, lateral acceleration sensors and tire/wheel sensors to determine the proper control action. These systems may also incorporate roll-rate sensors and roll angle estimation features in order to estimate rollover possibility during a maneuver and provide responsive control enhancement. A balance typically needs to be provided between controlling the vehicle roll motion and the vehicle yaw motion to provide improved vehicle response. Thus, it is usually necessary to detect certain vehicle conditions to provide improved vehicle control enhancement.
Vehicle enhancement control can be designed using output feedback. However, typically state-feedback based designs generally can provide more freedom in design and achieve higher potentials in performance. Furthermore, activation of vehicle control usually requires monitoring of vehicle states. However, in many cases, not all of the vehicle states are measured because of various disadvantages, such as sensor costs, implementation difficulties, etc. Therefore, it is common to estimate vehicle states for rollover reduction purposes.
Estimation of vehicle states, such as yaw-rate, lateral velocity and roll-rate has been investigated in the art for the development of vehicle stability enhancement in the yaw plane. Because of this, the focus has been on the estimation of the vehicle lateral motion instead of the roll motion, which is of particular interest in rollover reduction.